Continuous film treating device



y 1938 G. SCHUBERT 2,124,085

CONTINUOUS FILM TREATING DEVICE Filed Aug. 31, 1934 Patented July 19;1938 PATENT OFFICE- CONTINUOUS FILM TREATING DEVICE Georg Schubert,Berlin Germany, assignor to the firm Fernseh Aktien-Gesellschaft,Zehlendorf,

near Berlin, Germany Application August 31,

1934, Serial No. 742,259

In Germany August 31, 1933 2 Claims.

This invention relates to a continuous film developing and resensitizingprocess, particularly adaptable to intermediate film television systems,and involves the use of an endless film band and continuous emulsioncoating.

My invention provides for making a photographic record on a materialwhose sensitive layer arranged on an endless carrier is renewed beforeeach exposure and removed again after the pictorial impression has beenutilized.

The device required for carrying out this process comprises a pluralityof units. By way of example, one form of such a device is illustrated inthe accompanying drawing, in which Figure 5 l is a diagrammatic view ofthe treating device, illustrating also its application totelevision,Figure 2 shows a partially sectional side view, and Figure 3 shows apartially sectional end view of the casting unit.

Referring to the drawing, -l is the endless carrier or base whichsuccessively passes under the emulsion coating means 2, through thedrying chamber 26, the exposing device 29, the photochemical apparatuswith developer 30 and 25 fixing bath 32, the picture projecting device35,

the washing device 36 and the drying chamber 39 whence it moves againunder the coating means 2.

Standard cinematographic film consisting of 30 a mixture of celluloseesters and softening agents like camphor, etc. serves preferably as baseor carrier for the sensitive layer. It is advisable to render thesurface of this film carrier as hard as possible to prevent scratchesand also as flexible as possible so that it will withstand the fre-'quent stresses due to changes from moisture to dryness or warm to cold.It has been found that a standard cinematographic film band of the kindserving for instance as base for films to 40 be shown in cinema theatersis excellently suited for the purpose stated, as it will stand beingpassed hundreds of times through the projector,

though films twice or several times as thick as a standard film or evenmetal bands may be used.

As it is not advisable with respect to transparency, etc. to choosefilms that are too thick, the reinforcement, according to the invention,can be effected solely in the perforation or the latter may be providedwith a metal insertion 50 whereas the remainder of .the film is of thestandard type. The same effect could be attained also by arching orthickening the edges of the perforation by a special process.

The film band is preferably fed by-means' of 65 the perforation, theform of which is immaterial.

In view ofthe fact that the driving parts, such as sprockets, etc., havebeen standardized by the industry in question, it is best of course touse the perforation found in standard cinematographic film, though aparticularly broad perforation would enlarge the working surface of theteeth and thus insure better preservation of the material.

The difiiculties arising in connection with the application of theemulsion are due to the necessity of providing for absolutely uniformthickness of the sensitive layer in both transverse and runningdirection of the carrier. The latter is preferably coated only in thecenter between the rows of perforations, the coating consisting forinstance of the known halogen silver emulsion, so as to avoid soilingthe driving parts by particles of the emulsion dropping through theholes and thus passing to the back of the carrier.

Of the various types of casters used in coating a spouted device asshown in Figure 2 has been found to be best suited for the requirementsof the invention, as it gives the least trouble with respect to theformation of air bubbles in the emulsion and, above all, permits thecasting of a layer of any desired degree of thinness. It should be takeninto consideration that the film band possesses also at the castingpoint the same high speed of 24 frames per second as in -the cameraitself and that such a speed is unusual in coating and much higher thanthat employed in raw film works. The film band l'passes preferablyhorizontally under the spout of the caster 2 at a slight distancethereof amounting to less than 1 mm., e. g., 0.1 mm. or less. To providefor accurate adiustment of the thickness of the layer either the caster2 or the roller 9 over which the film band I passes, or both theseparts, are disposed so as to be universally adjustable and rotatable. InFigure 2, I have shownthe roller 9-supported by a yoke Ill terminatingat its lower end in a universal joint, which may take the-form ofrecessed side plates ll, held together by a bolt and thumbscrew l2 foradjustment, the side plates engaging a rounded nob l4 terminating theyok l0, and one of said side plates ll being fixedly attached, tosuitable supporting means I5, since it is necessary to provide fordisplaceability in vertical and horizontal direction as well as forrotatability so as to make it possible tov dispose the casting outletand the roller parallel to one another at any time or to compensateunevennesses in the film.

It has been found by experiments that when gelatin layer and to whichthe emulsion will adhere well and perfectly uniformly without causingany trouble during the subsequent removal of the layer by washing.

The invention is, however, not restricted to employing ready-made filmpretreated in the factory with intermediate coating, but permits, as aparticularly advantageous feature, the insertion of the step ofintermediate coating in the continuous process and the current supply ofa fresh intermediate coating to the washed film. For this purpose atreating device similar to that hereinafter described may be used, andmay engage the film I before it passes over roller 9.

It has further been found that the film lies not always perfectly levelunder the caster 2 in spite of being drawn over a counter-roller 8, butusually bends up slightly, so that the distance between the spout andthe film band is slighter in the center than at the edges. This willresult in uneven coating, the emulsion being thicker at the edges thanin the center. This defect can be overcome by a corresponding curving ofthe spout of the caster, as shown in Figure 3.

The vessel Ii for applying the emulsion is preferably made of two partsand consists of the airtight reservoir I1 and the casting device I9, thereservoir and the casting vessel being in communication by means of apipe. The casting vessel, unlike the reservoir for the emulsion, isdeaerated, and the deaerating pipe 2| is arranged so that no light canreach the emulsion 22, the pipe 2| being preferably of spiral form. Thereservoir II as well as the casting vessel I9 are disposed in the vesselI6, which is heat-insulated, and which may be electrically heated byheating coil 24 and controlled by adjustable contact-thermometer 25.

Differences in level between the reservoir and the contents of thecasting vessel are equalized by the pipe connecting the two members, thepipe starting at the bottom of the reservoir I1 and descending graduallyto the surface of the emulsion liquid 22 in the casting 'vessel It.Inthis way emulsion liquid is automatically supplied from the reservoirII, the air entering the connecting pipe when the level of the emulsion22 in" the caster I9 is dropping, and travelling in the form of singlebubbles towards the reservoir I! to change place with the emulsion. Thisstrictly automatic arrangement has given absolute satisfaction and makesit possible to keep constant the height of the emulsion in the casterand thus the pressure head.

A critical point is the maintenance of the casting temperature, as theviscosity of the emulsion constituting a gelatin solution depends ofcourse very much on temperature. Care should be taken to prevent unduecooling of the spout itself by arranging large masses of metal near itby constructing it for instance from a compact metal block. Ifnecessary, additional heating may be provided for at the outlet itself,and it is further possible of course to increase the viscosity of theemulsion by lowering the temperature. In this case, however, both thecasting vessel and the reservoir have to be subjected to increasedpressure. An increase in viscosity affords the advantage that the amountof emulsion coming out depends not so much on the adhesion andattraction of the band passing under the casting vessel but on the formof the spout.

The carrier film I provided with the sensitive layer enters a dryingdevice comprising a lighttight box 26 in which a plurality of drivingrolls 21 are arranged so that the film I passes, say, in spiral formthrough the space.

In another construction several driving rolls are arranged side by sideon the same shaft and the film moves to and fro' between this and asecond similar arrangement. A number of such arrangements may beprovided one on top of the other or combined in other ways and jointlyinstalled in a drier.

The rolls are arranged preferably so that the film band is not doing anyconsiderable crossing, and are of a type which permits the film band tolie thereon only with the perforated edges. To

latter are polished. v

Whether all rolls or only a part thereof are I driven depends on thelength of the film band to be fed, though it is advisable to restrict asmuch as possible the number of driven rolls driving the film band bymeans of perforation-engaging teeth so as to render the driving meansnot too compli- ,cated. All driven rolls must of course rotate uniformlyby driving them from a single synchronous motor. To insure convenientthreading of the film into the drying plant, the rolls are ar-- rangedon supports having hearings on one side only and the entire support forthe rolls can be withdrawn from the drying chamber as a unit, preferablyeven in parallel guides.

The emulsion is dried either by cooling or by means of air of normaltemperature but high speed. It may be advisable to free the air used fordrying from part of its liquid by cooling it below the dew point andthen heating it to normal or higher temperature so as to reduce therelative moisture and thus accelerate evaporation and the drying of theemulsion.

As very great amounts of air are required for the vaporization of theemulsion moisture, rapid ventilators are used which will remaineflicient even at a counter-pressure up to 500mm. water column. In viewof the retardation due to the numerous air pipings, such resistancesmust be expected. Ventilation, cooling and drying by means of heat mayalso be combined.

:The employment of mechanical wipers has been found to be impossible, asstated, as the emulsion is not scratch-proof when not dried. Drying byair current can be replaced by chemical drying, e. g., by means of saltsolutions of high osmotic pressure, alcohol, etc. If alcoholic dryingagents are used, the alcohol may be employed also as carrier ofhardening agents for the emulsion.

As the blowers cause a considerable noise, sound-proof enclosures,should be provided by covering the blowers for instance with severalhoods which are screened from each other as well as from the body of theapparatus by means of felt, rubber, etc. The drawn-in air travelspreferablya path whereby the silencing effect is enhanced still more.The outgoing air of the drier can be used for 'coolingother units of thegeneral device, such as the projector, the Kerr cell, thescanning orimage forming devices, and the film band is therefore preferably guidedin a narrow channel from the drier to the treating apparatus. Thesefeatures are not shown in detail. since working. It is they are largelyconventional, and are not claimed as part of the present invention. Thedried film is now ready for exposure. A conventionalized lens system29'focuses upon the film the image of a scene from a televisionreceiver, or the lens system may be a camera.

As the camera, no special construction is required, and a standardcinematographic camera will suffice as a rule. It is of course advisableto choose the feed rolls driven by the Maltese cross as large aspossible and thus distribute the transmission of power over a pluralityof perforations. This arrangement reduces the strain on the perforationsand increases the life of the film which has to pass so many timesthrough the apparatus. It is possible to replace the feed member drivenby the Maltese cross by a gripper, though, for the reasons.stated,.thiswould not be so favorable as the other arrangement.

Special care is required in the construction of the gate to insureabsolutely'plane guiding of the film in the gate without damaging thefresh emulsion. These two requirements can be met by choosing forinstance a size of image equal to one-half standard size at the samespeed of change and using standard film as carrier for the emulsion. Bysuitable guiding, the picture can then be held perfectly level in thegate, as on both sides thereof, in addition to the perforations,sufficient space will be available for tight guiding of the film withoutinjuring the emulsion.

With respect to the picture producing implements, all recording meansknown in connection with television and sound films may be used forrecording the picture on the film band, e. g., directly controlledbeacons or indirectly con trolled light, such as are light. As picturecomposing means, a perforated plate or reflecting wheels or similarlyacting devices may be used.

Having been exposed, the film band I enters the developing and fixingbaths 3|] and 32 containing the liquids required for thephotochemicalpicture production and, as in the drier, passes over a plurality ofrolls 3! which are displaced relative to one another in multiple loops.The driving and reversing rolls 3| are made of a material which is notafictedby the chemicals of the treating liquids. For .this reason,chromium-alloy steels or Monel metal are used, or rubber-covered metalcenters. Thecontainer for the liquid is made either of wood or, stillbetter, of metal that is proof against attacks by chemicals, orenamelled receptacles may be employed.

Since the quality of the picture produced depends also on thetemperature of the developing liquid, etc., the temperature of thedeveloper should be kept constant. The temperature to be maintaineddepends upon special conditions of known for instance to considerablyreduce the time required for obtaining a pictorial impression by raisingthe temperature of the developer to 22-23 C., though, on the other hand,increases in temperature involve the risk of fogging. The determinationof the most suitable temperature is a matter of experience. In thedevice according to the invention the developing and fixing tanks arearranged in a large water bath surrounded by tap water. It might beadvisable of course in some cases to cool not only the outer walls ofthe receptacles but to arrange also cooling coils inside the baths. Itis, further, suitable to move the treating liquids within the vessels soas to provide for the quick compensation of dilutions due to chemicalreaction. It is particularly necessary to avoid enrichment of thedeveloping bath by 'bromoions whichconsiderably interfere withdevelopment. To prevent this enrichment the developer may constantlyreceive a fresh supply of liquid or a large amount of developer liquidmay be kept in constant circulation. This applies also to the liquids ofthe fixing bath, though the requirements are not so stringent. I

The still moist film band coming out of the fixing bath is ready forfurther use, as for scanning at the transmitting end or for projectionat the receiving end of a television device, and the invention thereforedoes not provide for drying. Scanning or projection of the film bandmight be carried out also under liquid.

Special care is needed in the construction of the wipers which removethe liquids from the film and prevent for instance the carrying of thedeveloper into the fixing bath, etc. In view of the perfectly freshpictorial layer on the film it has been found necessary to dispense withall mechanical stripping means and to resort instead to clean air whichis blown over the film strips through nozzles 34. The liquid istherefore chiefly atomized and removed from the film by air pressure ina purely mechanical manner, and a suitable construction of the blowingdevice is of utmost importance to prevent any mechanical damage to theemulsion. The air used for blowing may be preheated, as compressed air,etc., is usually not available in movable plants. It is advisable toproduce the air current used for blowing by means of small blowers whichcan be readily installed within the general device. Special attentionshould be paid to keep this air free from finely distributed oilparticles usually found in compressed air, as otherwise re-coatingbecomes impossible.

The developed and fixed film is now ready for projection or scanning, inaccord with the use to which the film is put. For visual reproduction,the projector 35 should be of the usual type, though the sprocket forintermittent feed of the film is chosen as large as possible to reducedamage to the perforation to a minimum.

After scanning or projection, the film band passes to the washing outfit36 where the emulsion is removed from its carrier I and the film isarranged in the same way as in the developing apparatus.- It has beenfound suitable to accelerate the removal of the emulsion by means ofrotary brushes 31. For the same purpose, the washing water may beheated, or'a chemical solution, e. g., lye or gelatinliquefying agentslike thiosinamine, etc., may be used. As the emulsion passing into thewater will cause foaming if it enriches itself, the washing outfitshould be subdivided and the .water continually renewed incounter-current. The contents of the first washing chamber should bechanged frequently. It has been found advisable to provide for constanttemperature in the washing outfit by means of a thermostat andwater-bath, as working conditions depend upon temperature. Thesefeatures are conventional, and are not illustrated in the figure.

The drying device 39 for the carrier freed from its emulsion is similarto the one described for drying the freshly coated filmrwith thedifierence, however, that in this zone the film can be treated with hotair. The outgoing air of the first-mentioned drier 26 can thus be usedafter heating, and the drying chamber 39 is disposed under the drying Ithe air coming from the chamber 26 is positively device 26- in such away that,

forced to pass through an electric heater,- not shown, and then throughthe drying chamber 39.

As described already in connection with the drying outfit 26, the driveof all rolls is preferably arranged at only one side of the total plantto render the apparatus easily accessible. Unless driven directly, allrolls run in ball bearings, and all parts of the general device areclosed lighttight with the exception of the parts 35, 36 and I.

The device permits the rapid transmission of events being of specialinterest at the time for standard cinematographic projection. Thisbecomes possible, as the developed and finished picture can be used atthe receiving end for printing, either before or after projection, sothat a plurality of prints may be produced which by the same developingprocess can be transformed into finished films ready for release in theusual cinemas. This process is of importance in countries in which thelarger cities do not possess radio equipment. 7

I claim:-

1. A continuous film treating device. comprising a continuoustransparent film band. a caster and an opposed roller, said band passingtherebetween, said caster being concave to fit said roller, and beingslightly concave axially of said roller, means for adjusting theseparation between said roller and caster, an airtight reservoirconnected with said caster, so constructed and arranged as to maintainan emulsion stored within said reservoir always at uniform height insaid caster, and means for drawingsa id film past said caster at apredetermined rate, whereby emulsion coating of desired thickness isdeposited thereon.

2. In a device as set forth in claim 1, in which the margins of saidfilm band are provided with perforations adapted to be engaged bydriving projections on a driving means, said caster being formed toapply the emulsion only to the center portion of said film band, therebyleaving the perforated marginal portions bare.

GEORG SCHUBERT.

